Field of the Invention
The present invention relates to an article transport facility that includes: a plurality of article transport vehicles that travel along a travel path in only one direction to transport articles, and a transport control apparatus that controls each article transport vehicle.
Description of the Related Art
In factories and warehouses, automatic article transport using automatic guided vehicles (article transport vehicles) has been put into practice. In many cases, automatic guided vehicles autonomously travel along preset travel paths according to instructions and programs that are provided from a host control apparatus via communication. However, travel paths often include, for example, branching paths, converging paths, and intersecting paths, and therefore travel control is desired to be performed to prevent article transport vehicles from colliding with each other at, for example, a branching point, a convergence point, or an intersection point. JP 2000-250628A (Patent Document 1) discloses technology for setting control zones (control areas) that include such a branching point, a convergence point, an intersection point, or the like, and restricting article transport vehicles from entering the control zones based on predetermined conditions. Typically, the entrance of two or more article transport vehicles into such a control zone is restricted. (e.g. Patent Document 1: [0004], [0010], etc.)
For example, as shown in FIGS. 1 and 11 of Patent Document 1, in the case where a detour path (R3) is provided between two straight paths (R1 and R2) that are parallel to each other, a control zone (D1) is set to an area that includes: a branching point (A1) between one straight path (R1) and the detour path (R3); and a convergence point (B1) between the other straight path (R2) and the detour path (R3) in one aspect as shown in FIG. 11. In this case, the number of article transport vehicles that can enter the control zone (D1) is limited to one. Entrance into the control zone (D1) is restricted even in a simple case where two article transport vehicles respectively travel straight along the two straight paths (R1 and R2). Therefore, although there is no risk of a collision, either one of the article transport vehicles needs to wait, and thus the transport efficiency of the facility decreases as a whole. In view of such a problem, Patent Document 1 proposes that, as shown in FIG. 1 of Patent Document 1, a plurality of control zones (d1 and d2) should be set to such an area that includes a branching point and a convergence point. (Patent Document 1: [0021], [0022], FIG. 1, etc.)
Note that, even if a control zone is provided as shown in FIG. 1 of Patent Document 1, the number of article transport vehicles that can enter one control zone (d1 or d2 in the case of FIG. 1) at the same time is limited to one. However, in order to improve the transport efficiency of the facility as a whole, it is preferable to ease such a restriction in control zones while appropriately eliminating the risk of a collision or the like. Patent Document 1 also illustrates a mode in which whether or not to permit entrance into control zones is determined. (Patent Document 1: to [0026], FIG. 2, etc.) Such control of entrance into control zones (control areas) is, in some cases, performed via communication between: a control apparatus that controls whether or not an article transport vehicle is present in a control area, and the travel of each article transport vehicle; and article transport vehicles. Even in such cases, the number of article transport vehicles that can enter a control zone is typically fixed to a predetermined number (one in many cases). Therefore, regardless of what control is employed to control entrance into control zones (control areas), there is demand for the easing of a restriction on control zones (control areas) while appropriately eliminating the risk of a collision or the like.